Enterocytes / Intestinal Epithelial Cells (IECs)

What Are Intestinal Epithelial Cells and Why Are They Important?

Enterocytes and other intestinal epithelial cells (IECs) form one of the body’s largest exposed surfaces. They integrate signals from the gut microenvironment with physiological information from the immune, cardiovascular, and nervous systems. The epithelium functions as an interface between the gut microbiome and the mucosal immune system and operates together with immune cells and the mesenchyme as a functional triad (7, 9, 14, 15)

Where Are Enterocytes and Other Intestinal Epithelial Cells Located?

Enterocytes are present in both the small intestine and the colon. Paneth cells and microfold (M) cells are found only in the small intestine. IECs therefore occupy distinct intestinal regions while contributing to epithelial defense, communication, and transport (10, 12, 16, 18)

What Are the Main Types and Functions of Intestinal Epithelial Cells?

The IEC compartment includes Enterocytes / Intestinal Epithelial Cells (IECs) (absorptive enterocytes), Paneth cells, and goblet cells. Their central role is to coordinate communication between gut microbes and immune cells. Enterocytes support nutrient uptake and absorption, lipid metabolism, and the handling of bile acids. Colonic enterocytes passively reabsorb secondary bile acids and return them to the liver (4, 5, 7, 8, 11)

How Do Intestinal Epithelial Cells Protect the Host from Gut Microbes?

IECs create physical and chemical barriers that separate the luminal microbial community from the mucosal immune system. They release biomolecules into both the mucosa and intestinal lumen that contribute to innate and epithelial immunity, helping regulate microbial contact with host tissues (1, 2, 3, 6, 14, 15)

Which Tight-Junction Proteins Seal Enterocytes?

Enterocytes are connected by dynamic tight-junction complexes at the apical region of neighboring cells. Major protein families include occludins, claudins, and junctional adhesion molecules (JAMs). These transmembrane proteins bind intracellular zonula occludens (ZO) proteins, which connect the junctional complex to the actin cytoskeleton and help maintain epithelial barrier integrity (1, 2, 3, 6)

Which Toll-Like Receptors Are Expressed by Intestinal Epithelial Cells?

IECs express Toll-like receptors TLR2, TLR3, TLR4/CD284, TLR5, and TLR9. TLR3 and TLR9 are also present on endosomal membranes. These innate immune receptors enable epithelial cells to detect microbial signals and initiate downstream defense and communication processes (2, 6, 13, 14, 15)

How Do Innate Immune Signals Recruit Immune Cells in the Intestine?

In the mature adult intestinal epithelium, stimulatory innate immune receptor signals promote the production of soluble mediators. These mediators can recruit myeloid cells as well as T and B cells, linking epithelial microbial sensing to mucosal immune coordination (2, 3, 6, 14, 15)

How Quickly Does the Intestinal Epithelium Renew?

The intestinal epithelium undergoes rapid physiological renewal, with near-continuous turnover every 3–5 days. Intestinal stem cells located in the crypts support this renewal and replenish differentiated epithelial cell population (16, 17, 18)

References

(1) Abreu et al. 2002 J. Biol. Chem. 277: 20431–20437
(2) Rhee et al. 2005 Proc Natl Acad Sci USA 102: 13610-13615
(3) Bogunovic et al. 2007 Am. J. Physiol. Gastrointest. Liver Physiol. 292: G1770–G1783
(4) Pardo-Camacho et al. 2018 Am J Physiol Gastrointest Liver Physiol 314: G247-G255
(5) Kayisoglu et al. 2021
(6) Bilinski et al. 2022 Biomedicines 10: 837
(7) Portincasa et al. 2022a Int. J. Mol. Sci. 23: 1105
(8) Mahapatro et al. 2021
(9) Öhman et al. 2015 Nat. Rev. Gastroenterol. Hepatol. 12: 36-49
(10) Bellono et al. 2017 Cell 170(1): 185-198
(11) Beumer et al. 2020 Endocr. Rev. 41: 695-706
(12) Janney et al. 2020
(13) Chairatana & Nolan 2017 Critical Reviews in Biochemistry and Molecular Biology 52(1): 45-56
(14) Schubert et al. 2017 Immunological Reviews 279: 23-35
(15) Fulde & Hornef 2014 Immunol Rev 260: 21-34
(16) van der Flier et al. 2009 Cell 136(5): 903-912
(17) Clevers 2013a Cell 154: 274
(18) Gerbe et al. 2012 Cell Mol Life Sci. 69: 2907-2917

see also:
CD284 (Toll-Like Receptor 4 (TLR-4)) & Enterocytes / Intestinal Epithelial Cells (IECs)
Enterocytes / Intestinal epithelial cells (IECs) & Toll-like receptor 2 (TLR-2)
Gut microbiota & immunity